I use to be a member of a show committee for a number of years and basicly the show societies have taken a bit of liberty with the rules. They where only to allow caravan club's who had there own insurance - public liability to "stop over" for no more then 24 hrs - this was the rule that the peak body allowed to be place into operating charter.
The problem was competition.....a club would ring up and wish to book for 2 nights and our grounds man would say sorry we're only allowed to let you stay for 24hrs - they would reply but XYZ showgrounds will let us stay 2 nights etc etc so next thing you know clubs are staying 3 days and and anyone with a van or trailer can use the grounds as well. It is very hard on the show committee's to raise enough money to maintain there grounds and becoming a de-facto camp ground is an easy way to get some $$$.
I agree if there is a caravan park in town the local showgrounds shouldn't be allowed to provide camping unless it charges the same fee's as the van park, the costs and regulations placed on a caravan park are never ending and local show grounds get most of there things done either by the local council or at a discounted price - take emptying of septic tanks, there is no rules on a showground about how many times there tanks need to be emptied and inspected plus some local councils empty there tanks for free but if it's a caravan park ....
I would love to see the figure's just here in QLD of how many caravan parks there were 10 years ago, 5 years ago, and today.
You don't have to live forever.....you just have to live.